primNumbers.sql

with recursive numbers(n) as (
  select n
  from generate_series(1,5000) s(n)
),
prim(n, step) as (
  select numbers.n, 2
  from numbers
  union
  select prim.n, prim.step + 1
  from prim
  where prim.step <= (select max(n) from numbers) and (prim.n = prim.step or mod(prim.n, prim.step) != 0)
),
primPrec(n, m) as (
  select prim.n, sum(prim.n) over (rows between 1 preceding and 1 preceding)
  from prim
  where prim.step = (select max(n) from numbers)
), 
primTwins(n, m) as (
  select n, m
  from primPrec
  where (n-m) = 2
)
select count(*)
from primTwins